These calculators are planning aids, not authorities. Every result depends on its inputs and assumptions — beam angle, refractive index, swim speed, rounding — and on field conditions that change. Check each figure against your own equipment's specifications and the conditions on the day before you rely on it underwater. The formula is shown beside every tool on purpose: understand the math and verify the result rather than trusting the number blindly. A recreational and educational aid — dive planning and safety remain your responsibility.
How wide a circle each sonar ping samples, and how far apart to run your lanes for gap-free coverage.
Holding a set distance underwater is easier with something physical than by eye. A line — or a marked rigid rod — cut to your lane spacing makes the lateral step-over at each Surveyor's Pivot a measured move, and the same line can sit in frame as a scale reference for the photogrammetry. Optional, cheap, and battery-free — but it puts a line in the water, so weigh the entanglement cost below.
A recreational and educational planning aid — not survey-grade. Footprint depends only on water depth and beam angle; your depth as a diver does not change it. Always round spacing down — extra overlap is free insurance; a gap is a hole in your map.
A flat port bends light, so your lens sees a narrower scene underwater than its air spec promises. This gives you the true underwater field of view — and the corrected frame width the Baseline tool needs.
The common "flat ports cut FOV by 25%" rule understates the loss for wide lenses. This tool computes the exact geometry from Snell's law, so the frame width W it produces is the value to carry into the Baseline tool — not the air-rated width. Dome ports largely escape this; the course assumes flat consumer housings.
How far to move between photos to hit your overlap target, and the camera interval that produces it at swim speed.
Photogrammetry is a high-shot-density discipline — 80% overlap means each point appears in roughly five frames. More overlap than planned is fine; less is not, so when in doubt set a slightly faster interval. Feed the underwater frame width here, not the lens's air-rated width.
Circling a target feature: the angular step between shots, and how many frames a full orbit needs to reconstruct it.
Δφ = B / r is the small-angle approximation — fine for the tight baselines photogrammetry uses. The frame count is a planning floor; the closure margin gives you overlap back to the first frame so the loop reconstructs cleanly.
Your real inputs become an honest limitations statement to publish with the map — stating what was measured, not what you hoped. Adapt the wording to your site before you publish.
A good statement names the test, not the hope: it reports the measured checkpoint residual, names the dominant error sources, states what the map is good for, and explicitly disclaims what it is not. A missing or unverified scale reference is a stated limitation — never a silent gap.